Publications and other reference materials referred to herein are numerically referenced in the following text and respectively grouped in the appended Bibliography which immediately precedes the claims.
A Fiber Bragg Grating (FBG) is periodic modulation of the fiber core refractive index, typically, a few millimeters long [1]. FBG's have a variety of commercial applications. In optical communication as wavelength filtering and add\drop multiplexers, in fiber lasers as reflective mirrors, in fiber sensors as very sensitive temperature and strain gauges, and in many more fields. All FBG's that are used today are permanent gratings inscribed in a fiber. Once they are written they cannot be “removed”. Recently, there is a growing interest in FBG's for optical switching applications. Several works reported an implementation of an optical switch by tuning a pre-inscribed grating by means of heat stress and other relatively slow processes [2-5]. These methods are also based on permanent fiber gratings, and have several drawbacks due to inherent physical properties of their operation, which limits their applicability and performance. In the wider context, there have been several reports on switching of various photonic crystal structures both for fundamental and applicative purposes, see e.g., [6] for some recent reviews. In addition, several publications reported on transient Bragg gratings in gas for purposes of spectroscopy and in bulk semiconductors for studying free carrier recombination rates etc. [7]. However, to the best of our knowledge, no transient Bragg gratings in a fiber/waveguide (i.e., transient FBG) have been reported so far.
It is therefore a purpose of the present invention to provide a method of producing transient Bragg gratings in a fiber/waveguide.
It is another purpose of the present invention to provide examples of applications of the transient Bragg gratings obtained using this method.
Further purposes and advantages of this invention will appear as the description proceeds.